The proposed work is a series of studies concerned with neurosecretory hormones extracted from the crustacean eyestalk. These hormones are (1) hyperglycemic, causing a rise in concentration of glucose in the blood (2) gonad-inhibiting and (3) molt-inhibiting. Hyperglycemic hormones from different species show a species-specificity in their activity. Amino acid compositions of purified hormones will be compared to determine whether the species-specificity is explainable on this basis.